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Diffstat (limited to '')
| -rw-r--r-- | tex/testbench.tex | 1 | ||||
| -rw-r--r-- | tex/vhdl.tex | 78 |
2 files changed, 49 insertions, 30 deletions
diff --git a/tex/testbench.tex b/tex/testbench.tex index 36af6c7..edb2cbd 100644 --- a/tex/testbench.tex +++ b/tex/testbench.tex @@ -113,3 +113,4 @@ assert (tb_y = '0') report "error at vector 11" severity error; \end{lstlisting} \subsection{A simple but complete Test Bench} + diff --git a/tex/vhdl.tex b/tex/vhdl.tex index d6b12e5..cb2b389 100644 --- a/tex/vhdl.tex +++ b/tex/vhdl.tex @@ -44,8 +44,8 @@ In VHDL the concept of \emph{entity} describes a black box of which only inputs and outputs are known. The internals of an entity are described through an \emph{architecture}. There can be multiple architectures for a single entity. -\begin{center} - \ttfamily +\begin{figure}[h] + \centering \begin{tikzpicture}[ node distance = 1mm, pin/.style = { @@ -53,6 +53,7 @@ an \emph{architecture}. There can be multiple architectures for a single entity. inner sep = 0pt, minimum size = 2mm, }, ] + \ttfamily \node[ rectangle, draw = black, thick, fill = gray!20!white, minimum width = 4.5cm, minimum height = 4cm, @@ -79,7 +80,8 @@ an \emph{architecture}. There can be multiple architectures for a single entity. \node[right] at (pinr1) {Pin}; \end{tikzpicture} -\end{center} + \caption{An entity is a black box, that can have multiple architectures.} +\end{figure} Entities are declared with \vhdl{port()} that may contain a list of pins. Pins have a mode that can be \vhdl{in} input (only LHS\footnote{Left hand side}), @@ -120,8 +122,9 @@ From external libraries other types are available: \item \vhdl{std_ulogic} same as the previous but \emph{unresolved}. \end{itemize} The above are from the \vhdl{ieee.std_logic_1164} library, and can take the -values described in the following table. -\begin{center} +values described in table \ref{tab:std-logic-1164-types}. +\begin{table}[h] + \centering \begin{tabularx}{\linewidth}{>{\ttfamily}c l X} \toprule Value & Meaning & Usage \\ @@ -137,29 +140,15 @@ values described in the following table. - & Don't care & Allow minimization \\ \bottomrule \end{tabularx} -\end{center} + \caption{ + Possible values for \vhdl{std_logic} signals. + \label{tab:std-logic-1164-types} + } +\end{table} For the \emph{resolved} types, i.e. \vhdl{std_logic} types, when a signal is -multiply driven the conflict is resolved according to the table below. -Unresolved types will give a synthesization error. -\begin{center} - \ttfamily - \begin{tabular}{c|ccccccccc} - \toprule - & U & X & 0 & 1 & Z & W & L & H & - \\ - \midrule - U & U & U & U & U & U & U & U & U & U \\ - X & U & X & X & X & X & X & X & X & X \\ - 0 & U & X & 0 & X & 0 & 0 & 0 & 0 & X \\ - 1 & U & X & X & 1 & 1 & 1 & 1 & 1 & X \\ - Z & U & X & 0 & 1 & Z & W & L & H & X \\ - W & U & X & 0 & 1 & W & W & W & W & X \\ - L & U & X & 0 & 1 & L & W & L & W & X \\ - H & U & X & 0 & 1 & H & W & W & H & X \\ - - & U & X & X & X & X & X & X & X & X \\ - \bottomrule - \end{tabular} -\end{center} -A good example is a tri-state bus: +multiply driven the conflict is resolved according to table +\ref{tab:std-logic-1164-resolve}. Unresolved types will give a synthesization +error. A good example is a tri-state bus: \begin{lstlisting}[language=vhdl] architecture tristate of buscontrol is begin @@ -174,6 +163,31 @@ begin end process; end architecture tristateout; \end{lstlisting} +\begin{table}[h] + \centering + { + \ttfamily + \begin{tabular}{c|ccccccccc} + \toprule + & U & X & 0 & 1 & Z & W & L & H & - \\ + \midrule + U & U & U & U & U & U & U & U & U & U \\ + X & U & X & X & X & X & X & X & X & X \\ + 0 & U & X & 0 & X & 0 & 0 & 0 & 0 & X \\ + 1 & U & X & X & 1 & 1 & 1 & 1 & 1 & X \\ + Z & U & X & 0 & 1 & Z & W & L & H & X \\ + W & U & X & 0 & 1 & W & W & W & W & X \\ + L & U & X & 0 & 1 & L & W & L & W & X \\ + H & U & X & 0 & 1 & H & W & W & H & X \\ + - & U & X & X & X & X & X & X & X & X \\ + \bottomrule + \end{tabular} + } + \caption{ + Resolution table when a \vhdl{std_logic} signal is multiply driven. + \label{tab:std-logic-1164-resolve} + } +\end{table} \subsection{Declarations} \label{sec:declarations} Before a \vhdl{begin} -- \vhdl{end} block, there is usually a list of declarations. @@ -210,8 +224,8 @@ for `\reqph{label or {\tt all}}`: use entity `\reqph{library}`.`\reqph{entity}`( \end{lstlisting} \subsection{Concurrent Area} -\begin{center} - \ttfamily +\begin{figure}[h] + \centering \begin{tikzpicture}[ node distance = 1mm, pin/.style = { @@ -224,6 +238,7 @@ for `\reqph{label or {\tt all}}`: use entity `\reqph{library}`.`\reqph{entity}`( align = center, }, ] + \ttfamily \node[ draw = black, rectangle, fill = gray!20!white, thick, @@ -259,7 +274,10 @@ for `\reqph{label or {\tt all}}`: use entity `\reqph{library}`.`\reqph{entity}`( ; \end{tikzpicture} -\end{center} + \caption{ + In the concurrent area statements are not interpreted sequentially. + } +\end{figure} In the architecture between \vhdl{begin} and \vhdl{end}, the expressions are \emph{not} read sequentially, everything happens at the same time. |